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On November 29, 2013, the Environmental Protection Agency (EPA) finalized a suite of changes to the mandatory greenhouse gas (GHG) reporting rule; the changes were initially proposed on April 2, 2013, and go into effect on January 1, 2014. While updates were made impacting confidential business information and other technical or administrative changes, the most significant of the updates are the changes to previously used Global Warming Potentials (GWPs) for 26 GHGs. Many GWPs have been increased, which may increase the number of facilities subject to reporting requirements under the GHG mandatory reporting rule.

What are GWPs?

When it comes to the ability to trap heat in the Earth’s atmosphere, not all gasses are created equal. Global Warming Potentials, or GWPs, are values used to adjust GHG emissions for gases that are more efficient at trapping heat than others. Emissions are multiplied by the appropriate GWP to calculate CO2 equivalents, or CO2e.  

Changes to Table A-1

EPA has updated the GWPs based on values provided in the Intergovernmental Panel for Climate Change (IPCC)’s Fourth Assessment Report. EPA finalized the following changes to Table A-1, which lists the previous and updated GWPs for 23 GHGs:


NameChemical FormulaOld GWPNew GWPNet Change
Nitrous OxideN2O310298(12)
Sulfur HexafluorideSF623,90022,800(1,100)
HFC-32CH2 F265067525
HFC-41CH3 F15092(58)
HFC-125C2 HF52,8003,500700
HFC-134C2 H2 F41,0001,100100
HFC-134aCH2 FCF31,3001,430130
HFC-143C2 H3 F330035353
HFC-143aC2 H3 F33,8004,470670
HFC-152aCH3 CHF2140124(16)
HFC-227eaC3 HF72,9003,220320
HFC-236faC3 H2 F66,3009,8103,510
HFC-245ca C3 H2 F6560693133
HFC-43-10meeCF3 CFHCFHCF2 CF31,3001,640340
PFC-116C2 F69,20012,2003,000
PFC-218C3 F87,0008,8301,830
PFC-3-1-10C4 F107,0008,8601,860
PerfluorocyclobutaneC-C4 F88,70010,3001,600
PFC-4-1-12C5 F127,5009,1601,660
PFC-5-1-14C6 F147,4009,3001,900


Any facilities or suppliers that become subject to GHG reporting as a result of the change in these GWP values must commence the required recordkeeping and monitoring on January 1, 2014 and report in March 2015. Furthermore, operators that become subject to the GHG reporting rule as a result of these changes may utilize “Best Available Monitoring Methods” (or BAMM) until March 31, 2014; any requests to extend the use of BAMM must be submitted to EPA no later than January 31, 2014.

Reporters that are already subject to the reporting rule must use these updated GWPs in their calculations, which are due for submittal to EPA no later than March 31, 2014.

Republication of Existing Reports

In the preamble, the EPA clarified that reporters will not be required to revise GHG reports from previous years with the revised GWPs from this rulemaking action. Instead, EPA will publish a supplemental version of the CO2e emissions for reporting years 2011 through 2012 that will not supersede any of the submitted data. This will, “allow the Agency and public to view and compare trends in GHG data…without placing additional burden on reporters.”

[1] Federal Register, November 29, 2013; Page 71937